March 2, 2011

Where Have All The Sunspots Gone?

Researchers today provided the first computer model explaining the recent period of decreased solar activity during the Sun's 11-year cycle.

This recent solar minimum was the deepest observed in about 100 years.

The solar minimum has repercussions on the safety of space travel and the amount of orbital debris our planet accumulates.

NASA said that scientists around the world were puzzled by the extended disappearances of sunspots in 2008 through 2009.

"Plasma currents deep inside the sun interfered with the formation of sunspots and prolonged the solar minimum," lead author Dibyendu Nandi of the Indian Institute of Science Education and Research in Kolkata wrote in Thursday's edition of Nature.

The sun's magnetic field weakened during this deep solar minimum, which allowed for cosmic rays to penetrate the solar system in record numbers.

The decrease in ultraviolet radiation causes Earth's upper atmosphere to cool and collapse, according to a statement released by NASA.

As a consequence, space debris stopped decaying and started accumulating in Earth orbit due to increased atmospheric drag.

Observations from NASA's Solar Dynamics Observatory (SDO) will eventually provide measurements that could validate the current model and provide the basis for future solar cycle prediction.

"This research demonstrates how observations from Heliophysics System Observatory missions stimulate new theories and advance modeling techniques," Richard Fisher, director of the Heliophysics Division in NASA's Science Mission Directorate at the agency's headquarters in Washington, said in a statement.

NASA's Living With a Star Program and the Department of Science and Technology of the government of India funded the research.

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Image 1: This visible-light photograph, taken in 2008 by NASA's Solar and Heliospheric Observatory (SOHO) spacecraft, shows the Sun's face free of sunspots. The Sun experienced 780 spotless days during the unusually long solar minimum that just ended. New computer simulations imply that the Sun's long quiet spell resulted from changing flows of hot plasma within it. Credit: NASA/SOHO